I have a very smart air cooled RM500 in my workshop,I have been asked to make it road legal but its far too noisy for road use.Has anyone some ideas for shutting it up.It has a brand new DG full system on it which I have permission to chop up.Money is not an issue,time is so any bits that can be bought would be good,but not too worried if I have to spend a few hours with the Tig set.

Anyone ?

I would get a more modern silencer approved for enduro competition like an FMF Q stealth and make it fit. Maybe cruise ebay for a used stock KTM silencer?

Also try putting little bits of rubber between the fins on the barrel and head. A great deal of the noise from an air hammer is the fins resonating. Stuff wads of foam in the airbox (yeah, I know it kills the performance but induction noise is also a big problem on any large 2S). Try lagging the exhaust. Again a great source of noise is the expansion chamber resonating. By lagging it you will damp the noise level.

Edited September 30, 200916 yr by TooFastTim

Thanks for that,I'll have a look around on E-Bay.I was going to do the fins anyway as there is so much row there,not thought about the inlet so much,I'll see how it goes.I dont really want to cut up the new expansion box,but it acts like a big drum so I think it may have to be done,maybe make up a simple baffle inside to stuff some wadding into to keep the power pulses from acting direct onto the outside of the pipe.

I dont really want to cut up the new expansion box

Oh you don't need to cut the exhaust. Just get some industrial lagging material (used to be asbestos cloth) and wrap it, tightly, around the exhaust.

Seriously Jon, dont chop up the DG front pipe, it would be a real shame as they are the best aftermarket pipe around.

I have converted a lot of MXers to enduro use, definitely go for the alloy enduro tailpipe, it will make a huge difference. Ebay is the place to look, anything with the correct size entry hole.

On the Husky enduros from the mid 80's, they quietened the front pipes by using 2 heatshields, which were a piece of thin steel sheet, shaped to the same profile as the bulbous part of the pipe. They had one on the outside half and one inside, with exhaust padding in between and held in place with large jubilee clips. This reduced the sound from the front pipe dramatically, so worth considering if its still loud after you change the tail pipe.

Hope this helps

Martin

Good news - I've found the old original,(But very dented) front pipe off his spare bike.So with hopefully a larger enduro tailpipe and a lagged/covered front pipe it should be alot better. I'll chop up some fuel hose to damp the fins and see what its like.

Cheers for the ideas.